JP6579707B2 - Photosensitive resin composition for flexographic printing and flexographic printing original plate - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a flexographic photosensitive resin composition for use in a flexographic printing original plate or a photosensitive layer of a printing plate, and a flexographic printing original plate using the flexographic printing photosensitive resin composition.

Flexographic printing is a type of letterpress printing, and has the advantage that it can be applied to various types of printing materials because soft materials such as rubber and synthetic resin are used for the printing plate.
Printing plates used for flexographic printing have traditionally been made using a negative film and computer plate making technology (hereinafter referred to as CTP technology) that produces relief by directly drawing information processed on a computer into a printing plate. In recent years, CTP technology is becoming mainstream.
The original plate of the flexographic printing plate has different plate configurations when using a negative film and when using CTP technology. Both the case of using a negative film and the case of using CTP technology are common in that a photosensitive layer made of a photosensitive resin composition is provided on a substrate such as a PET resin, but the negative film is used. The case where the CTP technique is used differs from that formed on the photosensitive layer. First, when using a negative film, there is a transparent image carrier layer for protecting the negative film from the adhesiveness of the photosensitive layer. Before use, the negative film is brought into close contact with the transparent image carrier layer, and the photosensitive film is exposed from above the negative film. A relief image is formed by irradiating the layer with external radiation and removing uncured portions. On the other hand, when using the CTP technology, an infrared ablation layer is laminated on the photosensitive layer, and after drawing directly on the infrared ablation layer with a laser or the like, the photosensitive layer is irradiated with ultraviolet rays to remove the uncured portion, thereby relief. Form an image.
Recently, a relief image may be formed by removing the uncured portion with a developer containing water as a main component (water development).

By the way, in general, in a photosensitive resin printing original plate for flexographic printing capable of water-based development, a hydrophilic copolymer, a hydrophobic resin such as an elastomer, a polymerizable unsaturated monomer, etc. are provided on a support for maintaining dimensional accuracy. A photosensitive layer made of a photosensitive resin composition in which a monomer, a photopolymerization initiator, and the like are mixed is formed.
In the photosensitive resin composition used for such a photosensitive layer, it is preferable that each component in the composition is finely and uniformly dispersed in order to obtain a required image faithfully, and for shortening the plate making time. For this, it is preferable that the developing speed is high. Furthermore, since it is necessary to withstand the use of water-based ink after plate making and the attached ink must be washed away with water, it is preferable that the water swelling rate after curing is low, and naturally the printing durability is preferably high.

As a photosensitive resin composition that can be developed with water, for example, Patent Document 1 discloses a photosensitive resin composition containing an aqueous dispersion latex, a photopolymerizable monomer, rubber, and a photopolymerization initiator. Yes.
Patent Document 2 discloses a photosensitive resin composition that further contains a sulfonic acid-based surfactant and rubber forms a dispersed phase having a size of 10 μm or less.
Further, Patent Document 3 discloses a photosensitive resin composition in which an aqueous dispersion latex is synthesized by emulsion polymerization using a reactive emulsifier containing an unsaturated double bond and is internally crosslinked.

Japanese Patent No. 4211141 Japanese Patent No. 5325823 Japanese Patent No. 4627871

However, the water-based developable photosensitive resin compositions described in Patent Documents 1 and 2 have problems that the printing plate using the resin composition has low water resistance and that the printing durability after ink adhesion decreases.
On the other hand, the water-based developable photosensitive resin composition described in Patent Document 3 has a problem that the water-based developability is low although the water resistance and printing durability of the printing plate are high.

  As described above, a photosensitive resin composition used for a printing original plate for flexographic printing is required to have good developability with respect to an aqueous developer and water resistance and printing durability after forming a printing plate. It is difficult to achieve both.

  As a result of intensive studies on the photosensitive resin composition for flexographic printing by the present inventors, including a plasticizer component having a specific structure at the expense of water resistance and printing durability when used as a printing plate. Thus, the present inventors have found that developability with respect to an aqueous developer can be improved without completing the present invention.

That is, the present invention is as follows.
[1] At least
(A) a hydrophilic copolymer,
(B) an elastomer,
(C) a polymerizable unsaturated monomer,
(D) a plasticizer containing a repeating unit derived from a conjugated diene compound and containing a polymer having a carboxyl group in at least one kind of repeating unit; and
(E) a photopolymerization initiator,
A photosensitive resin composition for flexographic printing, comprising:
[2] The polymer containing a repeating unit derived from the conjugated diene compound and having a carboxyl group in at least one kind of repeating unit is a polymer obtained by copolymerizing an ethylenic carboxylic acid monomer. [1] The photosensitive resin composition for flexographic printing described in [3] further contains at least one compound (F) selected from the group consisting of a surfactant and a (meth) acrylic acid ester monomer having a polyalkylene glycol chain The photosensitive resin composition for flexographic printing according to [1] or [2].
[4] The method according to any one of [1] to [3], wherein a polymer ratio having a conjugated diene obtained by copolymerizing an ethylenic monocarboxylic acid monomer in the plasticizer (D) is 1 to 50% by mass. Photosensitive resin composition for flexographic printing.
[5] The elastomer (B) is 30 to 250 parts by mass, the polymerizable unsaturated monomer (C) is 10 to 200 parts by mass with respect to 100 parts by mass of the hydrophilic copolymer (A). The plasticizer (D) is 1 to 250 parts by mass, the photopolymerization initiator (E) is 0.1 to 50 parts by mass, a surfactant, and a (meth) acrylic acid ester monomer having a polyalkylene glycol chain. The photosensitive resin composition for flexographic printing according to any one of [1] to [4], wherein 0.1 to 15 parts by mass of at least one compound (F) selected from the group is contained.
[6] The photosensitive resin composition for flexographic printing according to any one of [1] to [5], wherein the elastomer (B) is a thermoplastic block copolymer.
[7] Any one of [1] to [6], wherein the hydrophilic copolymer (A) is an internally crosslinked polymer particle containing a unit derived from a reactive emulsifier containing an unsaturated double bond. The photosensitive resin composition for flexographic printing described.
[8] A flexographic printing original plate using the photosensitive resin composition for flexographic printing according to any one of [1] to [7].

  According to the present invention, it is possible to obtain a flexographic printing original plate that has high detergency with respect to an aqueous developer and has excellent ink resistance and printing durability.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. However, the present invention is not limited to this, and various modifications can be made without departing from the gist thereof. Is possible.

  In this embodiment, the photosensitive resin composition for flexographic printing has (A) a hydrophilic copolymer, (B) an elastomer, (C) a polymerizable unsaturated monomer, (D) a carboxylic acid, and a conjugated diene. It contains a plasticizer containing a polymer and (E) a photopolymerization initiator, and can be suitably used for a photosensitive resin composition layer of a flexographic printing original plate that is developed using an aqueous developer.

The hydrophilic copolymer (A) is an internally cross-linked polymer particle containing a unit derived from a hydrophilic unsaturated monomer. The unit derived from the hydrophilic unsaturated monomer may be, for example, 0.1 to 20% by mass, 0.5 to 15% by mass, or 1 to 10% by mass. Examples of such polymer particles include dispersion of polymer particles obtained by emulsion polymerization using a hydrophilic unsaturated monomer and, if necessary, other monomers copolymerizable therewith. Examples of the quality include those obtained by removing water from a water-dispersed latex dispersed in water.
The hydrophilic unsaturated monomer is preferably a monomer containing at least one hydrophilic group and an unsaturated double bond, for example, carboxylic acid, sulfonic acid, phosphoric acid or the like or a salt or acid anhydride thereof. Monomers containing unsaturated double bonds, etc., monomers containing hydroxyl groups and unsaturated double bonds, monomers containing acrylamide and unsaturated double bonds, containing reactive unsaturated double bonds Surfactant (monomer) etc. are mentioned. These compounds may be used alone or two or more of them may be used simultaneously. Such water-dispersed latex is not particularly limited. For example, polybutadiene latex, natural rubber latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, polychloroprene latex, polyisoprene latex, polyurethane latex, Examples thereof include water-dispersed latex polymers such as (meth) acrylate-butadiene latex, vinylpyridine polymer latex, butyl polymer latex, thiocol polymer latex, and acrylate polymer latex. And monobasic acids such as carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, vinyl benzoic acid and cinnamic acid, sulfonic acids such as styrene sulfonic acid, itaconic acid, fumaric acid, Maleic acid, citraconic acid, acidic functional group-containing unsaturated monomers such as dibasic acids such as muconic acid is also preferred that copolymerized 1 or more.
In addition to the polymer particles obtained by emulsion polymerization using a hydrophilic unsaturated monomer and, if necessary, other monomers that can be copolymerized therewith, the water-dispersed latex. Furthermore, other polymer particles may be included as a dispersoid. Examples of such other polymers include polybutadiene, natural rubber, and styrene-butadiene copolymer.

  The hydrophilic copolymer (A) preferably has a viscosity at 60 ° C. of 5000 poise or more. Further, the hydrophilic copolymer (A) preferably further has a toluene gel fraction of more than 10%.

Among these, an aqueous dispersion latex containing a butadiene skeleton or an isoprene skeleton in the molecular chain is preferable from the viewpoint of printing durability. Specifically, polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, and / or their water-dispersed latex are (meth) acrylic acid esters, acrylic acid, methacrylic acid, itaconic acid, etc. Those obtained by copolymerizing are preferred. More preferably, a copolymer of styrene-butadiene copolymer obtained by copolymerizing one or more kinds of unsaturated monomers containing acidic functional groups such as (meth) acrylic acid ester, acrylic acid, methacrylic acid, and itaconic acid. It is a water-dispersed latex.
It is preferable that the usage-amount of an acidic functional group containing unsaturated monomer is 1-30 mass% among the unsaturated monomers whole quantity used for the synthesis | combination of a hydrophilic copolymer (A). When the amount is 1 mass or more, aqueous development tends to be facilitated. On the other hand, when the amount is 30 mass% or less, the amount of moisture absorption of the photosensitive resin composition increases or the amount of ink swelling increases. It can prevent that the workability at the time of mixing of a composition deteriorates.

  Examples of unsaturated monomers other than acidic functional group-containing unsaturated monomers that can be used for the synthesis of the hydrophilic copolymer (A) include conjugated dienes, aromatic vinyl compounds, (meth) acrylic acid esters, hydroxyl groups. Ethylene-based monocarboxylic acid alkyl ester monomer, unsaturated dibasic acid alkyl ester, maleic anhydride, vinyl cyanide compound, (meth) acrylamide and derivatives thereof, vinyl esters, vinyl ethers, vinyl halides, Examples include basic monomers having an amino group, vinyl pyridine, olefins, silicon-containing α, β-ethylenically unsaturated monomers, and allyl compounds.

More specifically, conjugated dienes include 1,3-butadiene, isoprene, 2,3-dimethyl 1,3-butadiene, 2-ethyl-1,3-butadiene, 2-methyl-1,3-butadiene, Examples thereof include 1,3-pentadiene, chloroprene, 2-chloro-1,3-butadiene, cyclopentadiene and the like.
Examples of aromatic vinyl compounds include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, vinyltoluene, vinylxylene, bromostyrene, vinylbenzyl chloride, and pt-butyl. Examples include styrene, chlorostyrene, alkylstyrene, divinylbenzene, trivinylbenzene, and the like.

  As (meth) acrylic acid ester, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, n -Amyl (meth) acrylate, isoamylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, cyclohexyl (meth) acrylate, Phenyl (meth) acrylate, benzyl (meth) acrylate, 2-ethyl-hexyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxy Chlohexyl (meth) acrylate, glycidyl (meth) acrylate, ethylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butylene glycol di (meth) Acrylate, propylene glycol di (meth) acrylate, 1,5-pentanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, Triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate , Pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, allyl (meth) acrylate, bis (4-acryloxypolyethoxyphenyl) propane, methoxypolyethylene glycol ( (Meth) acrylate, β- (meth) acryloyloxyethyl hydrogen phthalate, β- (meth) acryloyloxyethyl hydrogen succinate, 3-chloro-2-hydroxypropyl (meth) acrylate, stearyl (meth) acrylate, phenoxyethyl (Meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, 2-hydroxy-1,3-di (meth) acryloxypropane, 2,2-bis [4-((me ) Acryloxyethoxy) phenyl] propane, 2,2-bis [4-((meth) acryloxy-diethoxy) phenyl] propane, 2,2-bis [4-((meth) acryloxy-polyethoxy) phenyl] propane, isobornyl Examples include (meth) acrylate.

Examples of the ethylene monocarboxylic acid alkyl ester monomer having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, and 1-hydroxy acrylate. Propyl, 1-hydroxypropyl methacrylate, hydroxycyclohexyl (meth) acrylate, and the like.
Examples of the unsaturated dibasic acid alkyl ester include crotonic acid alkyl ester, itaconic acid alkyl ester, fumaric acid alkyl ester, maleic acid alkyl ester, and the like.
Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile.
Examples of (meth) acrylamide and derivatives thereof include (meth) acrylamide, N-methylol (meth) acrylamide, N-alkoxy (meth) acrylamide and the like.
Examples of vinyl esters include vinyl acetate, vinyl butyrate, vinyl stearate, vinyl laurate, vinyl myristate, vinyl propionate, and vinyl versatate.
Examples of vinyl ethers include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, hexyl vinyl ether and the like.
Examples of vinyl halides include vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, and vinylidene fluoride.
Examples of the basic monomer having an amino group include aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and the like.
Examples of the olefin include ethylene.
Examples of the silicon-containing α, β-ethylenically unsaturated monomer include vinyltrichlorosilane and vinyltriethoxysilane.
Examples of the allyl compound include allyl ester and diallyl phthalate.
In addition, monomers having three or more double bonds such as triallyl isocyanurate can also be used.

  These monomers may be used alone or in combination of two or more. The mass ratio of the conjugated diene and other monomers is preferably between 5/95 and 95/5, more preferably 50/50 to 90/10. If this range is exceeded, the rubber elasticity of the photosensitive resin composition for flexographic printing may be deteriorated.

The hydrophilic copolymer (A) is preferably synthesized by emulsion polymerization, and in this case, a reactive emulsifier is preferably used as an emulsifier (surfactant) used during polymerization.
The reactive emulsifier contains a radical polymerizable double bond, a hydrophilic functional group and a hydrophobic group in the molecular structure, and has an emulsifying, dispersing, and wetting function like a general emulsifier, When the hydrophilic copolymer (A) is emulsion-polymerized, the average particle size is less than 0.1 parts by mass with respect to 100 parts by mass of the unsaturated monomer excluding the reactive emulsifier. An emulsifying (surfactant) agent capable of synthesizing a 5-500 nm polymer is preferred.
Examples of the structure of the radical polymerizable double bond in the molecular structure include a vinyl group, an acryloyl group, and a methacryloyl group. Examples of hydrophilic functional groups in the molecular structure include anionic groups such as sulfuric acid, nitric acid, phosphoric acid, boric acid, and carboxyl groups; cationic groups such as amino groups; polyoxyethylene, polyoxymethylene, Examples include polyoxyalkylene chain structures such as polyoxypropylene; or hydroxyl groups. Examples of the hydrophobic group in the molecular structure include an alkyl group and a phenyl group.
The reactive emulsifier includes an anionic emulsifier, a nonionic emulsifier, a cationic emulsifier, an amphoteric emulsifier, and the like depending on the structure type of the hydrophilic functional group contained in the structure. In addition, the radical polymerizable double bond, the hydrophilic functional group and the hydrophobic group in the molecular structure may each be included in a plurality of types.

  Of those that can be used as reactive emulsifiers in the present embodiment, those commercially available are shown below. Examples of anionic surfactants include Adekaria Soap SE (Asahi Denka Kogyo), Aqualon HS, BC, KH ( Daiichi Kogyo Seiyaku, Latemul S (Kao), Antox MS (Nippon Emulsifier), Adekaria Soap SDX and PP (Asahi Denka Kogyo), Haitenol A (Daiichi Kogyo Seiyaku), Eleminol RS (Sanyo Chemical Industries), Examples of nonionic surfactants such as spinomer (Toyo Soda Kogyo) include Aqualon RN, Neugen N (Daiichi Kogyo Seiyaku), Adekaria Soap NE (Asahi Denka Kogyo), etc., but are not limited thereto. Absent. These may be used alone or in combination of two or more.

  In this embodiment, it is preferable that the usage-amount of a reactive emulsifier is the range of 1-20 mass parts with respect to 100 mass parts of hydrophilic copolymers (A) calculated from the preparation amount of a raw material. When the amount of the reactive emulsifier is 1 part by mass or more, the image reproducibility of the obtained printing plate tends to be improved, and when it is 20 parts by mass or less, the printing resistance of the obtained printing plate tends to improve. is there.

In this embodiment, when a hydrophilic copolymer (A) is synthesize | combined by emulsion polymerization, a non-reactive emulsifier can also be used as needed.
Here, as the non-reactive emulsifier used as necessary, for example, anionic surfactants such as fatty acid soap, rosin acid soap, sulfonate, sulfate, phosphate ester, polyphosphate ester, salicozate acyl; Cationic surfactants such as nitrified fat derivatives, fat derivatives, fatty acid derivatives, α-olefin derivatives; alcohol ethoxylates, alkylphenol ethoxylates, propoxylates, aliphatic alkanolamides, alkyl polyglycosides, polyoxyethylene sorbitan fatty acid esters, oxy Nonionic surfactants such as ethyleneoxypropylene block copolymers are exemplified. These may be used alone or in combination of two or more.
As sulfonates, alkyl sulfonates, alkyl sulfates, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates, sulfonated oils, alkyl diphenyl ether disulfonates, α-olefin sulfonates, alkyl glyceryl ether sulfonates , N-acylmethyl taurate, and the like.
Other examples of these surfactants include those described in “Surfactant Handbook (Takahashi, Namba, Koike, Kobayashi: Engineering Books, 1972)”.
It is preferable that the usage-amount of a non-reactive emulsifier is less than 1 mass part with respect to 100 mass parts of hydrophilic copolymers (A) calculated from the preparation amount of a raw material. When the amount is less than 1 part by mass, the resulting printing plate exhibits an appropriate water swell ratio, and it is possible to prevent a decrease in abrasion resistance at the time of ink adhesion and a decrease in image reproducibility after moisture absorption.

As a method for emulsion polymerization of the hydrophilic copolymer (A), a predetermined amount of water, an emulsifier and other additives are charged in advance into a reaction system prepared at a polymerizable temperature, and a polymerization initiator and an unsaturated monomer are added to this system. In general, a monomer, an emulsifier, a regulator, and the like are added to the reaction system by batch operation or continuous operation. It is also a commonly used method that a predetermined amount of seed latex, an initiator, an unsaturated monomer, and other adjusting agents are charged in advance in the reaction system as necessary.
It is also possible to change the layer structure of the hydrophilic copolymer particles to be synthesized step by step by devising a method of adding unsaturated monomers, emulsifiers, other additives and modifiers to the reaction system. is there.
In this case, the physical properties representative of the structure of each layer include hydrophilicity, glass transition point, molecular weight, crosslinking density, and the like. Further, the number of steps of this layer structure is not particularly limited.

In this embodiment, a known chain transfer agent can be used for the polymerization of the hydrophilic copolymer (A). For example, as a chain transfer agent containing elemental sulfur, alkanethiol such as t-dodecyl mercaptan and n-dodecyl mercaptan; thioalkyl alcohol such as mercaptoethanol and mercaptopropanol; thio such as thioglycolic acid and thiopropionic acid Alkyl carboxylic acids; thiocarboxylic acid alkyl esters such as thioglycolic acid octyl ester and thiopropionic acid octyl ester; sulfides such as dimethyl sulfide and diethyl sulfide. In addition, examples of the chain transfer agent include halogenated hydrocarbons such as terpinolene, dipentene, t-terpinene, and carbon tetrachloride. Among these, alkanethiol is preferable because it has a high chain transfer rate and a good physical property balance of the resulting polymer.
These chain transfer agents may be used alone or in combination of two or more. These chain transfer agents are mixed with the monomer and supplied to the reaction system, or are added alone in a predetermined amount at a predetermined time. The amount of these chain transfer agents used is preferably 0.1 to 10% by mass based on the total amount of unsaturated monomers used for the polymerization of the hydrophilic copolymer (A). Below this range, the workability when mixing the photosensitive resin composition may deteriorate, and above this range, the molecular weight may be significantly reduced.

In this embodiment, a polymerization reaction inhibitor can be used for the polymerization of the hydrophilic copolymer (A) as necessary.
A polymerization reaction inhibitor is a compound that decreases the radical polymerization rate by being added to an emulsion polymerization system. More specifically, they are a polymerization rate retarder, a polymerization inhibitor, a chain transfer agent having a low radical restart reactivity, and a monomer having a low radical restart reactivity. The polymerization reaction inhibitor is generally used for adjusting the polymerization reaction rate and adjusting the physical properties of the latex. These polymerization reaction inhibitors are added to the reaction system by batch operation or continuous operation. When a polymerization reaction inhibitor is used, the strength of the latex film is improved and the printing durability is improved. Although the details of the reaction mechanism are unknown, it is presumed that the polymerization reaction inhibitor is closely related to the three-dimensional structure of the polymer, which is effective in adjusting the physical properties of the latex film.
Examples of polymerization reaction inhibitors include quinones such as o-, m-, or p-benzoquinone; nitro compounds such as nitrobenzene, o-, m-, or p-dinitrobenzene; amines such as diphenylamine; Catechol derivatives such as tributylcatechol; 1,1-disubstituted vinyl compounds such as 1,1-diphenylethylene or α-methylstyrene, 2,4-diphenyl-4-methyl-1-pentene; 2,4-diphenyl And 1,2-disubstituted vinyl compounds such as -4-methyl-2-pentene and cyclohexene. In addition, polymerization is carried out in “POLYMER HANDBOOK 3rd Ed. (J. Brandup, EH Immergut: John Wiley & Sons, 1989)”, “Revised Polymer Synthesis Chemistry (Otsu: Kagaku Dojin, 1979.)”. Examples thereof include compounds described as inhibitors or polymerization inhibitors. Among these, 2,4-diphenyl-4-methyl-1-pentene (α-methylstyrene dimer) is particularly preferable from the viewpoint of reactivity. These polymerization reaction inhibitors may be used alone or in combination of two or more.
The amount of these polymerization reaction inhibitors used is preferably 10% by mass or less based on the total amount of unsaturated monomers used for the polymerization of the hydrophilic copolymer (A). Above this, the polymerization rate may be significantly reduced.

The radical polymerization initiator is one that initiates addition polymerization of monomers by radical decomposition in the presence of heat or a reducing substance, and both inorganic and organic initiators can be used.
Examples of such compounds include water-soluble or oil-soluble peroxodisulfates, peroxides, azobis compounds, and the like. Specifically, potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, Examples thereof include hydrogen oxide, t-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisbutyronitrile, cumene hydroperoxide, and others, and POLYMER HANDBOOK (3rd edition), J. Org. Brandrup and E.I. H. Examples thereof include compounds described in Immergut, published by John Willy & Sons (1989). In addition, a so-called redox polymerization method in which a reducing agent such as acidic sodium sulfite, ascorbic acid or a salt thereof, erythorbic acid or a salt thereof or Rongalite is used in combination with a polymerization initiator may be employed. Of these, peroxodisulfate is particularly suitable as the polymerization initiator. The amount of the polymerization initiator used is usually selected from the range of 0.1 to 5.0% by mass, preferably from the range of 0.2 to 3.0% by mass, based on the mass of all unsaturated monomers. . Below this range, stability during synthesis of the hydrophilic copolymer may not be obtained, and above this range, the moisture absorption of the photosensitive resin composition may increase.

  In this embodiment, various polymerization regulators can be added as needed during the synthesis of the hydrophilic copolymer (A). For example, a pH adjuster such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium hydrogen carbonate, sodium carbonate, disodium hydrogen phosphate can be added as a pH adjuster. Further, various chelating agents such as sodium ethylenediaminetetraacetate can also be added as a polymerization regulator. Other additives include alkali-sensitive latex, thickeners such as hexametaphosphoric acid, water-soluble polymers such as polyvinyl alcohol and carboxymethyl cellulose, thickeners, various anti-aging agents, ultraviolet absorbers, preservatives, and bactericides. Add various additives such as antifoaming agents, dispersants such as sodium polyacrylate, water resistance agents, metal oxides such as zinc white, crosslinkers such as isocyanate compounds and epoxy compounds, lubricants, water retention agents, etc. No problem. The addition method of these additives is not particularly limited, and can be added during the synthesis of the hydrophilic copolymer regardless of after the synthesis.

  In this embodiment, the polymerization temperature in the case of emulsion polymerization of the hydrophilic copolymer (A) is usually selected in the range of 60 to 120 ° C., but the polymerization is performed at a lower temperature by the redox polymerization method or the like. Also good. Further, as a redox catalyst, a metal catalyst such as a divalent iron ion, a trivalent iron ion, or a copper ion may coexist.

  The hydrophilic copolymer (A) is preferably in the form of particles, and the average particle size is preferably 500 nm or less, particularly preferably 100 nm or less. If the average particle size is too large, the aqueous developability of the resulting printing original plate may be lowered.

Moreover, it is preferable that the toluene gel fraction of a hydrophilic copolymer (A) is 60 to 99%. If the gel fraction is below this range, the strength of the printing plate obtained is lowered, and if it exceeds this range, the mixing properties of the hydrophilic copolymer (A) and the elastomer (B) tend to be remarkably lowered.
Here, the toluene gel fraction refers to a hydrophilic copolymer obtained by suspending an appropriate amount of a dispersion of about 30% by mass of the hydrophilic copolymer (A) on a Teflon sheet and drying it at 130 ° C. for 30 minutes. 0.5 g of (A) was taken, immersed in 30 ml of toluene at 25 ° C., shaken for 3 hours using a shaker, filtered through 320 SUS mesh, and the non-passing portion was dried at 130 ° C. for 1 hour. The mass fraction (%) obtained by dividing the subsequent mass by 0.5 (g).

  In the present embodiment, the (B) elastomer is an elastomer that exhibits rubber elasticity at room temperature (25 ° C.), and examples thereof include a thermoplastic block copolymer, polybutadiene, polyacrylonitrile-butadiene, and a polyurethane elastomer. Of these, a thermoplastic block copolymer is preferred.

The thermoplastic block copolymer is preferably obtained by polymerizing a monovinyl-substituted aromatic hydrocarbon monomer and a conjugated diene monomer. Examples of the monovinyl-substituted aromatic hydrocarbon monomer include styrene, α-methylstyrene, and p-methyl. Styrene, p-methoxystyrene and the like are used, and butadiene, isoprene and the like are used as the conjugated diene monomer.
Specific examples include styrene-butadiene-styrene block copolymers and styrene-isoprene-styrene copolymers. Here, in the styrene-butadiene-styrene block copolymer or the styrene-isoprene-styrene copolymer, a diblock body such as a styrene-butadiene copolymer or a styrene-isoprene copolymer may be mixed. . Further, styrene and butadiene or isoprene may be randomly copolymerized on the butadiene part or isoprene part in the styrene-butadiene-styrene block copolymer or styrene-isoprene-styrene copolymer.
Here, if the content of the monovinyl-substituted aromatic hydrocarbon unit in the elastomer (B) is too low, a cold flow of the photosensitive resin composition is caused and good thickness accuracy cannot be obtained. The hardness of the printing plate becomes too high, and good print quality cannot be obtained. Therefore, it is preferably in the range of 8 to 50% by mass.

The vinyl bond unit in the conjugated diene segment of the elastomer (B) contributes to improving the reproducibility of the relief, but at the same time, increases the tackiness of the flexographic printing plate surface. From the viewpoint of balancing these two characteristics, the average ratio of vinyl bond units is preferably 5 to 40% by mass, and more preferably 10 to 35% by mass.
The average content of monovinyl-substituted aromatic hydrocarbon units and conjugated diene units and the average ratio of vinyl bond units in the conjugated diene segment of the elastomer (B) can be determined by IR spectrum or NMR.

The content of the elastomer (B) is preferably 30 parts by mass or more and less than 250 parts by mass with respect to 100 parts by mass of the hydrophilic copolymer (A). More preferably, it is 30 parts by mass or more and less than 200 parts by mass. More preferably, it is 50 mass parts or more and less than 170 mass parts.
When the amount is less than 30 parts by mass, the printing durability tends to decrease and the swelling ratio of the polar ink tends to increase. When the amount is 250 parts by mass or more, the developability to an aqueous developer tends to decrease. .

  Examples of the polymerizable unsaturated monomer (C) used in the present embodiment include carboxylic acid esters such as acrylic acid, methacrylic acid, fumaric acid and maleic acid, acrylamide and methacrylamide derivatives, allyl ester, styrene, and the like. Examples thereof include N-substituted maleimide compounds.

Specific examples thereof include diacrylates and dimethacrylates of alkanediols such as hexanediol and nonanediol, or ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, butylene glycol diacrylate and dimethacrylate, or Trimethylolpropane triacrylate and trimethacrylate, pentaerythritol tetraacrylate and tetramethacrylate, N, N′-hexamethylenebisacrylamide and methacrylamide, styrene, vinyltoluene, divinylbenzene, diacrylphthalate, triallyl cyanurate, Fumaric acid diethyl ester, fumaric acid dibutyl ester, fumaric acid dioctyl ester, fumaric acid Acid distearyl ester, butyl octyl fumarate, diphenyl fumarate, dibenzyl fumarate, dibutyl maleate, dioctyl maleate, bis (3-phenylpropyl) fumarate, dilauryl fumarate, fumarate Examples include acid dibehenyl ester, N-laurylmaleimide and the like.
These may be used alone or in combination of two or more.

  The content of the polymerizable unsaturated monomer (C) is preferably 10 parts by mass or more and less than 200 parts by mass with respect to 100 parts by mass of the hydrophilic copolymer (A). More preferably, it is 20 to 150 mass parts, More preferably, it is 30 to 100 mass parts. If it is less than 10 parts by mass, there is a tendency to reduce the formation of fine dots and characters. In addition, when the amount is 200 parts by mass or more, deformation during storage and transportation of the uncured plate increases, or the hardness of the obtained plate increases, and printing on a printing medium with poor surface quality having surface irregularities. There is a tendency to cause adverse effects such as impairing the ink loading of the solid portion.

The photosensitive resin composition for flexographic printing of this embodiment contains a polymer having a repeating unit derived from a conjugated diene compound as a plasticizer (D) and having a carboxyl group in at least one kind of repeating unit. . Specific examples of the conjugated diene compound include butadiene and isoprene.
In the polymer, the carboxyl group may be contained in a repeating unit derived from a conjugated diene compound, or may be contained in a different repeating unit. That is, the polymer may be produced, for example, by polymerizing a conjugated diene compound and then modifying the resulting polymer with a carboxylic acid, or copolymerizing a monomer having a carboxyxyl group and a conjugated diene compound. You may manufacture by. Specific examples of the monomer having a carboxylxyl group include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, phthalic acid, acrylic acid ester, methacrylic acid ester, acrylic acid salt, methacrylic acid salt and the like. Derivatives.
Further, the polymer has a repeating unit derived from a conjugated diene, and if it has a carboxyl group in at least one kind of repeating unit, it further contains other repeating units such as a unit derived from acrylonitrile. You may do it.

  The polymer having a repeating unit derived from a conjugated diene compound and having a carboxyl group in at least one type of repeating unit is preferably a copolymer of a conjugated diene compound and an unsaturated monocarboxylic acid (derivative). Among them, those obtained by copolymerizing (meth) acrylic acid and / or (meth) acrylate, butadiene and / or isoprene, and acrylonitrile are preferable. The structure of the copolymer may be either random or block. More preferably, it is a terpolymer of (meth) acrylic acid, butadiene, and acrylonitrile.

The polymer having a repeating unit derived from a conjugated diene compound and having a carboxyl group in at least one kind of repeating unit preferably has a viscosity at 60 ° C. of less than 5000 poise, more preferably less than 3000 poise. is there. When the viscosity at 60 ° C. is 5000 poises or less, the plasticizing effect is increased.
The polymer having a repeating unit derived from a conjugated diene compound and having a carboxyl group in at least one type of repeating unit preferably further has a toluene gel fraction of 10% or less. When the toluene gel fraction is large, the viscosity increases and the plasticizing effect tends to decrease. In addition, a toluene gel fraction can be measured by the same method as the toluene gel fraction measuring method described in the place of the hydrophilic copolymer (A).
The polymer having a repeating unit derived from a conjugated diene compound and having a carboxyl group in at least one kind of repeating unit may be used alone or in combination.

The photosensitive resin composition for flexographic printing in this embodiment has a repeating unit derived from a conjugated diene as a plasticizer (D), and contains a polymer having a carboxyl group in at least one kind of repeating unit. And good detergency (developability with respect to an aqueous developer).
In this embodiment, the photosensitive resin composition for flexographic printing has a sea-island structure mainly composed of a phase containing a hydrophilic copolymer (A) and a phase containing an elastomer (B). Where the phase containing the polymer (A) starts as a starting point, a polymer having a structure similar to that of the hydrophilic copolymer (A) and having a hydrophilic carboxyl group is used as a plasticizer. Thus, the plasticizer (D) component is easily dispersed in the phase containing the hydrophilic copolymer (A), and as a result, the hydrophilicity of the phase containing the hydrophilic copolymer (A) in the resin composition. It is presumed that the degree of cleaning becomes higher, thereby improving the cleaning property.
However, it is not limited to this estimation.

In the photosensitive resin composition for flexographic printing of the present embodiment, the plasticizer (D) has a repeating unit derived from a conjugated diene, and in addition to a polymer having a carboxyl group in at least one type of repeating unit. Other plasticizer components can be contained.
Specific examples of other plasticizer components include hydrocarbon oils such as naphthene oil and paraffin oil, liquid polybutadiene, liquid polyisoprene, terminal acrylate of liquid polybutadiene, terminal hydroxy of liquid polybutadiene, terminal epoxy of liquid polybutadiene, and liquid acrylonitrile. -Butadiene copolymer, liquid styrene-butadiene copolymer, polystyrene having a number average molecular weight of 2,000 or less, sebacic acid ester, phthalic acid ester and the like. Among these, liquid polybutadiene, terminal acrylate of liquid polybutadiene, terminal hydroxy of liquid polybutadiene, terminal epoxy of liquid polybutadiene, liquid acrylonitrile-butadiene copolymer, and liquid styrene-butadiene copolymer are preferable.
The ratio of the polymer having a repeating unit derived from a conjugated diene to the total amount of the plasticizer (D) and having a carboxyl group in at least one kind of repeating unit is preferably 1% by mass or more and less than 50% by mass, More preferably, it is 2 mass% or more and less than 40 mass%, More preferably, it is 3 mass% or more and less than 30 mass%. If it is in the above range, it is preferable because the transparency before curing is high and the detergency can be improved.

  The amount of the plasticizer (D) with respect to 100 parts by mass of the hydrophilic copolymer (A) is preferably 1 part by mass or more and less than 250 parts by mass, more preferably 10 parts by mass or more and less than 220 parts by mass, still more preferably 20 parts by mass. As mentioned above, it is less than 200 mass parts. If the amount is less than 1 part by mass, the curing shrinkage after molding may increase, and if it is 250 parts by mass or more, the cold flow property may deteriorate.

  Examples of the photopolymerization initiator (E) used in this embodiment include benzophenone, Michler's ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, α-methylol benzoin, α-methylol. Benzoin methyl ether, α-methoxybenzoin methyl ether, benzoin phenyl ether, α-t-butylbenzoin, 2,2-dimethoxyphenylacetophenone, 2,2-diethiphenylacetophenone, benzyl, pivaloin, anthraquinone, benzanthra Examples include quinone, 2-ethylanthraquinone, and 2-chloroanthraquinone. These may be used alone or in combination of two or more.

(E) As content of a photoinitiator, 0.1 mass part or more and less than 50 mass parts are preferable with respect to 100 mass parts of hydrophilic copolymers (A). More preferably, it is 1 part by mass or more and less than 30 parts by mass. If the amount is less than 0.1 parts by mass, the formation of fine dots and characters is reduced, which is not preferable. On the other hand, when the amount is 50 parts by mass or more, an adverse effect of lowering the exposure sensitivity appears because the active light transmittance such as ultraviolet rays of the photosensitive resin composition is lowered.

In this embodiment, the photosensitive resin composition may further contain at least one compound (F) selected from the group consisting of a surfactant and a (meth) acrylic acid ester monomer having a polyalkylene glycol chain. it can.
Examples of the surfactant of the compound (F) that can be used in this embodiment include an anionic surfactant, an ionic surfactant, a nonionic surfactant, and a reactive surfactant.
Specifically, sodium polyoxyethylene styrenated phenyl ether sulfate, sodium polyoxyalkylene branched decyl ether sulfate, ammonium polyoxyethylene isodecyl ether sulfate, sodium polyoxyethylene tridecyl ether sulfate, sodium polyoxyethylene lauryl ether sulfate, poly Ammonium oxyethylene lauryl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene oleyl cetyl ether sulfate, sodium polyoxyethylene oleyl cetyl ether sulfate, polyoxyethylene tridecyl ether phosphate ester, polyoxyethylene alkyl (C2-C16) Ether phosphate ester, polyoxyethylene alkyl (C2-C16) ether Acid ester monoethanolamine salt, alkyl (C2-C16) phosphate sodium ester, alkyl (C2-C16) phosphate ester monoethanolamine salt, disodium lauryl sulfosuccinate, polyoxyethylene sulfosuccinate lauryl disodium, Polyoxyethylene alkyl (C2-C20) sulfosuccinate disodium, linear alkylbenzene sulfonate sodium, linear alkylbenzene sulfonate, alpha-olefin sulfonate sodium, phenol sulfonate, dioctyl sulfosuccinate sodium, sodium lauryl sulfate, higher fatty acid potassium salt Anionic surfactants such as alkyl (C8-C20) trimethylammonium chloride, alkyl (C8-C20) dimethylethylammonium Loride, Didecyldimethylammonium chloride, Lauryldimethylbenzylammonium chloride, Stearyldimethylhydroxyethylammonium paratoluenesulfonate, Stearyldimethylaminopropylamide, Tributylbenzylammonium chloride, Lauryldimethylaminoacetic acid betaine, Lauric acid amidopropyl betaine, Palm oil fatty acid amide Ionic surfactants such as propyl betaine, amidopropyl betaine octoate, lauryl dimethylamine oxide, polyoxyalkylene tridecyl ether, polyoxyethylene isodecyl ether, polyoxyalkylene lauryl ether, polyoxyalkylene alkyl ether, polyoxyalkylene A mixture of ether and polyether polyol, Reether polyol, polyoxyethylene sulfonated phenyl ether, polyoxyethylene naphthyl ether, phenoxyethanol, polyoxyethylene phenyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyethylene lauryl ether, polyoxyethylene oleyl cetyl ether, polyoxyethylene Lenoleic acid ester, polyoxyethylene distearic acid ester, polyoxyethylene glyceryl isostearate, polyoxyethylene hydrogenated castor oil, coconut oil fatty acid diethanolamide, polyoxyethylene alkylamine, sorbitan trioleate, sorbitan sesquioleate, sorbitan monooleate, Sorbitan monococorate, sorbitan monocaprate, polyoxyethylene sorbita Monococoate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, octyl polyglycoside, butyl polyglycoside, sucrose benzoate, sucrose acetate, sucrose fatty acid ester nonionic surfactant, polyoxy Anionic reactive surfactants such as ethylene-1- (allyloxymethyl) alkyl ether ammonium sulfate, polyoxyethylene nonylpropenyl phenyl ether ammonium sulfate, and nonionic reactive surfactants such as polyoxyethylene nonylpropenyl phenyl ether Can be mentioned.

  Moreover, as the (meth) acrylic acid ester monomer having a polyalkylene glycol chain of the compound (F) that can be used in the present embodiment, the polyethylene having a ethylene glycol chain in the range of 2 to 20 as a monomer having a polyalkylene glycol. Glycol mono (acrylate), polyethylene glycol di (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol di (meth) acrylate, polyethylene glycol chain and / or polypropylene glycol containing propylene glycol chain in the range of 2 to 20 Polyethylene glycol polypropylene glycol di (meth) acrylate, cresyl polyethylene glycol (meth) acrylate each containing 2 to 20 chains, Sulfonyl phenoxy polyethylene glycol (meth) acrylate, and the like.

The surfactant of compound (F) and the (meth) acrylic acid ester monomer having a polyalkylene glycol chain may be used alone or in combination of two or more.
Of these compounds (F), nonionic surfactants, nonionic reactive surfactants, and (meth) acrylic acid ester monomers having a polyalkylene glycol chain are preferred.
The content of the compound (F) is preferably 0.1 parts by mass or more and less than 15 parts by mass with respect to 100 parts by mass of the hydrophilic copolymer (A). More preferably, it is 0.5 mass part or more and less than 10 mass parts. When the amount is less than 0.1 parts by mass, the developability with respect to the aqueous developer tends to be low. When the amount is 15 parts by mass or more, the haze of the obtained resin composition is increased, or the drying time after development is increased. There is a tendency that the solvent resistance with respect to the water-based ink is reduced.

  In addition to the essential or optional components described above, the photosensitive resin composition for flexographic printing of the present embodiment may further include various auxiliary additive components such as a plasticizer, a thermal polymerization inhibitor, and an ultraviolet absorber. Antihalation agents, light stabilizers and the like can be added.

In this embodiment, the hydrophilic copolymer (A) can be used after removing water by various methods. Specifically, for example, after coagulation using a flocculant such as sulfate, nitrate, hydrochloride, carbonate, carboxylate, water may be removed by a dehydration process such as centrifugation and a drying process, or hydrophilicity After mixing the copolymer (A) alone or the hydrophilic copolymer (A) with at least one compound comprising a plasticizer (D), a compound such as a surfactant (F), a stabilizer, etc. The water may be removed by distillation or the like. As a method for removing water by distillation or the like, a batch type dryer such as a kneader, a nauter mixer, or ribocorn may be used, or a devolatilizing extruder, a thin film distillation machine, a CD dryer, a KRC kneader, an SC processor, or the like. A type dryer may be used.
Thus, at least one or more of the hydrophilic copolymer (A), or the hydrophilic copolymer (A) and the plasticizer (D), a compound such as a surfactant (F), a stabilizer, etc. After obtaining a dry product of the mixture, various known kneading devices such as an extruder, a Banbury mixer, a kneader and the like are used together with the elastomer (B), the polymerizable unsaturated monomer (C) and the photopolymerization initiator (E). The photosensitive resin composition can be prepared by kneading.
A photosensitive layer having a desired thickness can be formed from the obtained photosensitive resin composition by hot press molding, calendaring, extrusion molding or the like.

In the present embodiment, the flexographic printing original plate has at least a photosensitive layer comprising the photosensitive resin composition of the present embodiment or containing the photosensitive resin composition.
The flexographic printing plate precursor may be a laminate in which a photosensitive layer is provided on a support such as polyester in order to maintain accuracy as a printing plate.
Also, on the surface opposite to the support of the photosensitive layer, in order to improve the contact property with the infrared ablation layer or the negative film for drawing directly on the photosensitive layer, and to enable reuse of the negative film A flexible film layer (also referred to as a transparent image carrier layer or an anti-adhesion layer) that can be developed in an aqueous system may be provided.
The support, the infrared ablation layer, and the flexible film layer can be adhered to the photosensitive layer by roll lamination after the photosensitive layer is formed into a sheet shape, for example. After lamination, the surface accuracy of the photosensitive layer can be improved by further performing a heat press.

In this embodiment, examples of the active light source used for photocuring the photosensitive layer of the flexographic printing original plate (forming a latent image) include, for example, a low pressure mercury lamp, a high pressure mercury lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, a xenon lamp, A zirconium lamp, sunlight, etc. are mentioned.
In the present embodiment, a latent image is formed by irradiating light through an infrared ablation layer or a transparent image carrier after drawing on a photosensitive layer, and then a relief (removal) is performed by removing (developing) an unirradiated portion using an aqueous developer. A printing plate) is obtained.

The aqueous developer is a developer containing water as a main component, and may be water itself, for example, a nonionic or anionic surfactant in water, and, if necessary, a pH adjuster, You may mix | blend a washing | cleaning accelerator etc.
Specific examples of the nonionic surfactant include polyoxyalkylene alkyl or alkenyl ether, polyoxyalkylene alkyl or alkenyl phenyl ether, polyoxyalkylene alkyl or alkenyl amine, polyoxyalkylene alkyl or alkenyl amide, ethylene oxide / propylene oxide Examples include block appendages.
Specific examples of the anionic surfactant include linear alkylbenzene sulfonate having an alkyl having an average carbon number of 8 to 16, an α-olefin sulfonate having an average carbon number of 10 to 20, an alkyl group or an alkenyl group. A dialkyl sulfosuccinate having 4 to 10 carbon atoms, a sulfonate of a fatty acid lower alkyl ester, an alkyl sulfate having an average carbon number of 10 to 20, a linear or branched alkyl or alkenyl group having an average carbon number of 10 to 20 And alkyl ether sulfates having an average of 0.5 to 8 moles of ethylene oxide added, saturated or unsaturated fatty acid salts having an average carbon number of 10 to 22 and the like.
Examples of the PH adjuster include sodium borate, sodium carbonate, sodium silicate, sodium metasilicate, sodium succinate, sodium acetate, and the like. Sodium silicate is preferred because it is easily dissolved in water.

Further, a cleaning aid may be added to the developer. The cleaning aid is used in combination with the surfactant and the pH adjusting agent to enhance the cleaning (development) ability of the developer. Specific examples include amines such as monoethanolamine, diethanolamine and triethanolamine, ammonium salts such as tetramethylammonium hydroxide, and paraffinic hydrocarbons.
These can be used, for example, by adding to and mixing in the developer in the range of 0.1 to 50% by mass, preferably 1 to 10% by mass.

During development, the printing original plate may be supplementarily vibrated with ultrasonic waves or the like, or the surface of the printing original plate may be rubbed using a mechanical means such as a brush.
The developed printing plate is preferably dried in an oven at, for example, 50 ° C. for 15 to 120 minutes.
Depending on the composition of the photosensitive layer containing the photosensitive resin composition of the present embodiment, stickiness may remain on the plate surface even after drying. In that case, stickiness can be removed by a known surface treatment method. As such a surface treatment method, exposure treatment with actinic rays having a wavelength of 300 nm or less is desired.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

<Production Example 1: Synthesis of a hydrophilic copolymer (A) -containing mixture containing other plasticizers used in Example 1-5 and Comparative Example 1>
In a pressure-resistant reaction vessel equipped with a stirrer and a temperature control jacket, 125 parts by mass of water and (α-sulfo (1-nonylphenoxy) methyl-2- (2-propenyloxy) ethoxy-poly (oxy-) as a reactive emulsifier 1,2-ethanediyl) ammonium salt “ADEKA rear soap” (manufactured by Asahi Denka Kogyo Co., Ltd.) was initially charged, the internal temperature was raised to 80 ° C., styrene 10 parts by mass, butadiene 60 parts by mass, butyl An oily mixture of 23 parts by weight of acrylate, 5 parts by weight of methacrylic acid, and 2 parts by weight of acrylic acid and 2 parts by weight of t-dodecyl mercaptan, 28 parts by weight of water, sodium peroxodisulfate 2 parts by mass, sodium hydroxide 0.2 parts by mass, (α-sulfo (1-nonylphenoxy) methyl-2- (2-propenyloxy) ethoxy -An aqueous solution consisting of 2 parts by weight of ammonium salt of poly (oxy-1,2-ethanediyl) was added at a constant flow rate over 5 hours and 6 hours, respectively.
Subsequently, the temperature of 80 ° C. was kept as it was for 1 hour to complete the polymerization reaction, and then cooled. Further, after adjusting the pH of the produced copolymer latex to 7 with sodium hydroxide, unreacted monomers are removed by a steam stripping method, and the resultant is filtered through a 200 mesh wire net. An aqueous dispersion of the hydrophilic copolymer (A) used in the examples was obtained by adjusting the partial concentration to 40% by mass.
Further, with 100 parts by weight of this aqueous dispersion, 10 parts by weight of liquid polybutadiene [LBR352: made by Kuraray], which is another plasticizer, is mixed under reduced pressure at 80 ° C. and mixed with the hydrophilic copolymer (A). A mixed dried product of other plasticizers was obtained.

<Production Example 2: Synthesis of a hydrophilic copolymer (A) -containing mixture containing other plasticizers used in Example 6>
An aqueous dispersion of the hydrophilic copolymer (A) used in Example 6 was obtained in the same manner as in Production Example 1 except that sodium dodecylbenzenesulfonate, which is a non-reactive emulsifier, was used instead of the reactive emulsifier. . Using this, a dried mixture of the hydrophilic copolymer (A) and another plasticizer was obtained in the same manner as in Production Example 1.

<Production Example 3: Preparation of infrared ablation layer>
10 parts by mass of an ethylene-acrylic acid copolymer [SG-2000: manufactured by Lead City, 20% by mass aqueous solution] which is an anionic polymer having a carboxylic acid group as an anionic polar functional group, carbon black [BONJET CW-2: Orient Chemical Industry, 20% by mass aqueous solution] 5 parts by mass, release agent [KF-351: Shin-Etsu Chemical Co., Ltd.] 0.05 parts by mass, water 30 parts by mass, ethanol 15 parts by mass are mixed to form an ablation layer. A coating solution was obtained.
This ablation layer forming coating solution is coated on a PET film having a thickness of about 100 μm as a cover film so that the film thickness after drying is 3 μm, and subjected to a drying treatment at 90 ° C. for 2 minutes, A laminate of the ablation layer and the cover film was obtained.

Example 1
(1) Production of photosensitive resin composition 110 parts by mass of a mixture containing the hydrophilic copolymer (A) obtained in Production Example 1 and other plasticizer, and elastomer (B): styrene-butadiene-styrene copolymer 75 parts by mass of combined [D-KX405: made by Kraton] was mixed at 140 ° C. using a pressure kneader, and then 60 parts by mass of liquid polybutadiene [manufactured by LBR-352 Kuraray] and plasticizer (D): liquid carboxylic acid Modified NBR [DN-601 made by Nippon Zeon] 5 parts by mass, polymerizable unsaturated monomer (C): 1,9-nonanediol diacrylate 20 parts by mass and 1,6-hexanediol dimethacrylate 20 parts by mass, light Polymerization initiator (E): 2,2-dimethoxyphenylacetophenone 5 parts by mass and surfactant (F): [XL-100: manufactured by Daiichi Kogyo Seiyaku] 3 parts by mass, and 2,6- A mixture of 5 parts by mass of di-t-butyl-p-cresol was added little by little over 15 minutes, and the addition was completed and kneaded for another 20 minutes to obtain a photosensitive resin composition.

(2) Production of printing original plate The above composition was taken out, and a thickness of 100 μm thick polyester film (hereinafter abbreviated as PET) coated with an elastomer-containing adhesive and a 5 μm thick polyvinyl alcohol (PVA) layer was coated. Sandwiched between 100 μm thick PET, molded into a plate shape with a thickness of 1.14 mm using a press machine heated to 120 ° C., and then peeled off the PET coated with the PVA layer, and the support (PET) − A laminate comprising a photosensitive layer was obtained. The obtained laminate was laminated with the infrared ablation layer obtained in Production Example 3 in contact with the photosensitive layer to obtain a printing original plate.

(3) Manufacture of printing plate From the side of the printing original plate support (PET coated with adhesive), an ultraviolet exposure machine (JEOL Ltd.) so that the pattern height (RD) after curing is about 0.6 mm. It exposed using Seiki JE-A2-SS).
Next, the cover film of the infrared ablation layer was peeled off, drawn on the infrared ablation layer using an ESKO laser drawing machine (CDI), and then exposed from the infrared ablation layer side for 10 minutes with the exposure machine.
After the exposure, an aqueous solution of 1% Nissan soap (aqueous developer) was prepared and washed (developed) at 40 ° C. using a JEOL Seiki washer (JOW-A3-P) to remove unexposed portions. . The cleaning time is measured in advance by measuring the thickness d (mm) obtained by cleaning the unexposed printing original plate for 5 minutes and matching the desired pattern height (RD = 0.6 (mm)). , RD × d × 1.5 (min) was calculated as the time. After drying, it was post-exposed with an ultraviolet germicidal lamp or an ultraviolet chemical lamp to obtain a printing plate.

(4) Evaluation (a) Evaluation of washability (water developability) of printing original plate Filled with 1% aqueous solution of Nissan soap in a washing machine (JOW-A3-P) manufactured by JEOL Ltd., and the printing obtained in (2) The cover film of the original infrared ablation layer was peeled off and washed at 40 ° C. for 5 minutes.
The case where 0.5 mm or more was shaved was marked with ◎, the case where 0.3 mm or more and less than 0.5 mm was shaved, ○, 0.1 mm or more and less than 0.3 mm, and the case where the amount of shaving was less than 0.1 mm was marked with ×.

(B) Evaluation of solvent resistance of printing plate As a solvent resistance test for evaluating the resistance of the printing plate to water-based ink, the printing plate obtained in (3) was simulated in a 10% isopropyl alcohol aqueous solution at 23 ° C. It was immersed for 24 hours, and the mass increase rate (water expansion rate) (%) was measured.
When the mass increase rate was less than 2%, it was evaluated as ◯, and when it was 2% or more, it was marked as x.

(C) Evaluation of printing durability of printing plate In order to evaluate the strength of the printing plate (printing durability), a wear wheel (taper wear tester, hard wear wheel manufactured by Tester Sangyo) was used in a pseudo manner. A wear resistance test was conducted.
A printing plate having a solid surface was prepared in the same manner as in (2), and the obtained printing plate was immersed in a 10% isopropyl alcohol aqueous solution for 16 hours as a water-based ink substitute, and after 1000 rotations using a wear ring. The abrasion amount (mg / cm ² ) of the plate surface was measured. The amount of wear was determined by dividing the decrease (mg) in the mass of the printing plate by the area (cm ² ) where the wear ring contacts the solid part.
Abrasion loss of less than 2mg / cm ² ◎, less than 2 mg / cm ² or more 5mg / cm ² ○, and as × 5 mg / cm ² or more.

(D) Evaluation of transparency (Haze) of printing original plate The photosensitive resin composition was sandwiched between 100 μm-thick PET films subjected to a release treatment, and molded into a 3 mm-thick plate with a press machine heated to 120 ° C.
A Haze meter (NDH-5000) manufactured by Nippon Denshoku Industries Co., Ltd. was used, and the haze of a plate molded in an uncured state to a thickness of 3 mm was measured. A haze of 20 or less was evaluated as ◯, 20 or more and 30 or less as Δ, and 30 or more and 50 or more as x.
(E) Evaluation of image reproducibility before and after moisture absorption The photosensitive resin printing plate produced in (3) and the printing original plate produced in (2) are stored in a constant temperature bath at 40 ° C. and 80% humidity for 1 week, and (3) Similarly, a printing plate was produced. The white line width and depth of 500 μm were compared before and after moisture absorption. When the difference between the line width and the depth after moisture absorption is less than 5%, ◯ is indicated when the difference is 5% or more and less than 10%, and × when the difference is 10% or more.

(Example 2-5, Comparative Example 1)
Except for changing the content of the elastomer (B), polymerizable unsaturated monomer (C) and plasticizer (D), the type of (meth) acrylate monomer (F) containing surfactant or polyalkylene glycol In the same manner as in Example 1, a photosensitive resin composition having the composition shown in Table 1, and a flexographic printing original plate and a printing plate comprising the resin composition were obtained.
Table 2 shows the evaluation results of the obtained photosensitive resin composition, printing original plate and printing plate.

(Example 6)
As the hydrophilic copolymer (A), a photosensitive resin composition, and a flexographic printing original plate comprising the photosensitive resin composition, and a photosensitive resin composition in the same manner as in Example 1 except that the one obtained in Production Example 2 was used. A printed version was obtained.
Table 2 shows the evaluation results of the obtained photosensitive resin composition, printing original plate and printing plate.

(Comparative Example 2)
A photosensitive resin composition was obtained in the same manner as in Example 1 except that the hydrophilic copolymer (A) was not used.
Table 2 shows the evaluation results of the obtained photosensitive resin composition, printing original plate and printing plate.

  The resin composition for flexographic printing of the present invention can be suitably used as a material for a photosensitive layer of a flexographic printing original plate, particularly a flexographic printing original plate for aqueous development.

Claims (7)

at least,
(A) a hydrophilic copolymer,
(B) an elastomer,
(C) a polymerizable unsaturated monomer,
(D) a plasticizer containing a repeating unit derived from a conjugated diene compound and containing a polymer having a carboxyl group in at least one kind of repeating unit; and
(E) a photopolymerization initiator,
Containing
The polymer containing a repeating unit derived from the conjugated diene compound and having a carboxyl group in at least one type of repeating unit is a polymer obtained by copolymerizing an ethylenic carboxylic acid monomer, and has a viscosity at 60 ° C. Is less than 5000 poise,
The hydrophilic copolymer (A) has a viscosity at 60 ° C. of 5000 poise or more,
The polymerizable unsaturated monomer (C) is an acrylic acid ester having two acryloyl groups and / or a methacrylic acid ester having two methacryloyl groups ,
The elastomer (B) is an elastomer that exhibits rubber elasticity at room temperature (25 ° C.),
A photosensitive resin composition for flexographic printing , wherein the plasticizer (D) is a liquid carboxylic acid-modified NBR .   The photosensitive resin for flexographic printing according to claim 1, further comprising at least one compound (F) selected from the group consisting of a surfactant and a (meth) acrylic acid ester monomer having a polyalkylene glycol chain. Composition.   The photosensitivity for flexographic printing according to claim 1 or 2, wherein a polymer ratio having a conjugated diene obtained by copolymerizing an ethylenic carboxylic acid monomer in the plasticizer (D) is 1% by mass or more and less than 50% by mass. Resin composition.   The elastomer (B) is 30 parts by mass or more and less than 250 parts by mass, and the polymerizable unsaturated monomer (C) is 10 parts by mass or more and 200 parts by mass with respect to 100 parts by mass of the hydrophilic copolymer (A). Less than 1 part, the plasticizer (D) is 1 part by weight or more and less than 250 parts by weight, the photopolymerization initiator (E) is 0.1 part by weight or more and less than 50 parts by weight, a surfactant, and a polyalkylene glycol chain. The flexographic printing according to any one of claims 1 to 3, wherein at least one compound (F) selected from the group consisting of (meth) acrylic acid ester monomers is contained in an amount of 0.1 to 15 parts by mass. Photosensitive resin composition.   The photosensitive resin composition for flexographic printing according to any one of claims 1 to 4, wherein the elastomer (B) is a thermoplastic block copolymer.   The flexo according to any one of claims 1 to 5, wherein the hydrophilic copolymer (A) is an internally cross-linked polymer particle containing a unit derived from a reactive emulsifier containing an unsaturated double bond. Photosensitive resin composition for printing.   A flexographic printing original plate using the photosensitive resin composition for flexographic printing according to any one of claims 1 to 6.